| From | Sasha Levin <> | Subject | [PATCH AUTOSEL 4.19 097/100] nbd: fix possible sysfs duplicate warning | Date | Fri, 18 Oct 2019 18:05:22 -0400 |
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From: Xiubo Li <xiubli@redhat.com>
[ Upstream commit 862488105b84ca744b3d8ff131e0fcfe10644be1 ]
1. nbd_put takes the mutex and drops nbd->ref to 0. It then does idr_remove and drops the mutex.
2. nbd_genl_connect takes the mutex. idr_find/idr_for_each fails to find an existing device, so it does nbd_dev_add.
3. just before the nbd_put could call nbd_dev_remove or not finished totally, but if nbd_dev_add try to add_disk, we can hit:
debugfs: Directory 'nbd1' with parent 'block' already present!
This patch will make sure all the disk add/remove stuff are done by holding the nbd_index_mutex lock.
Reported-by: Mike Christie <mchristi@redhat.com> Reviewed-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Xiubo Li <xiubli@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk> Signed-off-by: Sasha Levin <sashal@kernel.org> --- drivers/block/nbd.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c index bc2fa4e85f0ca..d445195945618 100644 --- a/drivers/block/nbd.c +++ b/drivers/block/nbd.c @@ -228,8 +228,8 @@ static void nbd_put(struct nbd_device *nbd) if (refcount_dec_and_mutex_lock(&nbd->refs, &nbd_index_mutex)) { idr_remove(&nbd_index_idr, nbd->index); - mutex_unlock(&nbd_index_mutex); nbd_dev_remove(nbd); + mutex_unlock(&nbd_index_mutex); } } -- 2.20.1
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